Unmanned Systems Technology 007 | UMEX 2016 report | Navya ARMA | Launch & recovery systems | AIE 225CS | AUVs | Electric motors | Lethal autonomous weapons

82 April/May 2016 | Unmanned Systems Technology PS | Miniaturising cameras C entral to the operation of most unmanned systems is the use of one or more cameras (writes Stewart Mitchell). For many systems, particularly airborne ones, payload size and weight are key considerations, so can cameras be made smaller and lighter using emerging technology? Over recent years, camera technology has been the subject of an enormous amount of development, and these days lens technology is now the limiting factor for high-end camera systems. The quality of a lens is a function of the optical path length (OPL) of the light passing through it, and this determines the clarity and diffraction of the light as it travels through the lens and on to the light sensor. In one of the latest advances in this area, scientists at the Nano-Electro- Mechanical Systems Laboratory at the Australian National University, along with researchers from the University of Wisconsin, have created a lens with the highest ever level of OPL and which is only 0.67 nm thick. It is made from molybdenum disulphide (MoS 2 ), which is part of a class of materials known as chalcogenide glasses, and displays OPL properties orders of magnitude better than the current metamaterials used for high-end camera lenses. One of the Wisconsin researchers, Professor Jhu Wang, says, “Refractive optical components [lenses] rely on OPL to modify the phase front [wave frequency] of an optical beam so it can be interpreted by a camera. One would expect the OPL of a 2D monolayer material to be too small to have a significant impact on the phase front of the light, as the layer is atomically very thin. However, surprisingly, we found a giant OPL from a single-layer MoS 2 construction, which is more than 50 times greater than its physical thickness. “This enhancement is created by relatively strong multiple reflections at the air-to-MoS 2 interfaces, as the refractive index of single-layer MoS 2 is as high as 5 [compared with a current high-end glass lens refractive index of 1.9-2.0]. It offers the opportunity of controlling the phase front of an optical beam very effectively using only an atomically thin structure. Excited by this discovery, we came up with the idea of designing a convex lens using MoS 2 which, thanks to its high refractive index, provides extraordinary interaction with light.” Molybdenum disulphide also has the ability to manipulate the flow of light on an atomic scale with the introduction of electricity. Wang says, “The unique and broad tuneability of the refractive index with an electric field in layered MoS 2 enables atomically thin optical components such as micro-lenses with electrically tuneable focal lengths, and electrical tuneable phase [light wavelength] shifters with ultra-high accuracy, which cannot be realised by conventional bulk solids.” This lens quality and scale are ideal for use in ultra-compact imaging systems on a micro- or even nano-scale unmanned system. If this technology were to be integrated with advanced optical sensors of the same scale, it would mean that while we would not be able to see the cameras on unmanned systems of the future, they could see us in higher detail and from much further away than ever before. Now, here’s a thing “ ” The tuneability of the refractive index enables atomically thin optical components with tuneable focal lengths